Recently, various uses of a cylindrical film member formed of a thermoplastic resin or the like as an inner liner member of a pneumatic tire have been proposed. An unvulcanized tire is formed in such a way that the cylindrical film member is fitted onto a primary forming drum as described in Patent Document 1, and then an adhesive sheet member formed of an unvulcanized rubber, such as a tie rubber material or a carcass material, is further wound around the outer periphery of the cylindrical film member.
Meanwhile, in the above-described forming drum, multiple plates each having an arc-shaped cross section are generally arranged annularly around a drum axis to form a drum shell. In addition, the forming drum is configured to be capable of expanding/contracting the outer diameter thereof by causing these plates to advance and retreat in a radial direction. Operations in primary forming of an unvulcanized tire are as follows. Specifically, the cylindrical film member is fitted onto such an expandable/contractible forming drum, and an adhesive sheet member of a tie rubber material or the like is further adhered around the outer periphery of the cylindrical film member.
However, in a forming drum 1 having an expansion/contraction mechanism, splices and differences in level are formed on an outer peripheral surface of the forming drum 1 as shown in FIG. 5, because of plates constituting a shell. Hence, there is a problem that, when a cylindrical film member 3 is fitted onto the forming drum 1, the cylindrical film member enters a gap formed on the outer peripheral surface of the forming drum 1 due to a splice or a difference in level between the plates, which results in formation of an air pocket 6. When an adhesive sheet member 4 is adhered with such an air pocket 6 being present, tire failure may occur starting from the air pocket.